The present invention pertains generally to an apparatus and method of intercomputer communication, and more particularly to a low level message filter which provides content tag recognition and selection independent of the higher level processing occurring in an individual computing element. 2. Description of the Contemporary and/or Prior Art
As a result of the recent advances in solid-state circuit technology, distributed computer systems, using many smaller processors, is becoming a practical alternative to the highly centralized large-computer systems currently in use. Increased throughput, fault tolerance, inherent software modularity, and ease of system expansion are often mentioned as potential advantages of distributed over centralized architectures. However, most of the many possible distributed architectures are untried and, in general, each trades some advantages for others. Therefore, ease of system expansion, enabling one to accommodate many different computing elements on the same bus, is of particular interest.
Current distributed systems are costly to expand and upgrade and often require significant software module redesign and hardware interface redesign. The prior art does not teach a method of intercomputer communication which facilitates the integration of new systems with existing systems, and does not teach hardware message filtering responsive to the content of the data message.
Prior art devices, such as disclosed in U.S. Pat. No. 4,123,796 issued Oct. 31, 1978 to J. Y. Shih, utilize a transceiver connected to a data bus for communicating with a plurality of control devices. In the one-to-many communications system as taught by Shih, each module is given a unique address and the transceiver prefixes each data message by the address of the module, or modules, with which it wishes to communicate. The Shih reference does not teach the use of a content tag which allows each computer element to selectively receive data messages based on the relevancy of these date messages to the software modules processed by the computing element.
Similarly, U.S. Pat. No. 4,019,176 issued on Apr. 19, 1977 to Cour et al describes an intercomputer communication scheme in which all stations receive and select messages based on a "destination address code". The reference does not teach receiver selection based on the content of the data message.
The prior art does not teach the use of a low level message filter which processes content tags independent of the higher level processing occurring in an individual computing element.